When a breaker keeps tripping, the breaker is almost never the problem. It is the messenger. Something on that circuit is pulling more current than the wire can safely carry, or leaking current somewhere it should not go, and the breaker is doing the one job it exists for.
There are four causes, and you can usually narrow it down yourself before deciding whether this is a call-an-electrician situation or a move-the-space-heater situation.
The four reasons a breaker keeps tripping
Overload. The circuit is simply being asked for too much: a space heater and a kettle and a microwave sharing one kitchen circuit. The tell is timing. An overloaded breaker trips seconds to minutes after the load comes on, and stays on when you unplug things. This one is about how the circuit is used, and sometimes about a house that needs more circuits.
A short circuit. Hot touching neutral, somewhere in the wiring, a device, or something plugged in. The tell is that the trip is instant, every time. If resetting the breaker with everything unplugged still trips it immediately, stop resetting it. That is a fault in the wiring, and it is exactly the case where repeated resets do the damage.
A ground fault or arc fault. GFCI and AFCI breakers trip on things ordinary breakers ignore: current leaking to ground, often through moisture, or the signature of arcing at a loose connection. Outdoor circuits, bathrooms and older appliances are the usual suspects.
A failing breaker. They do wear out, and a breaker that trips at ever lighter loads or feels loose in the panel can be the fault itself. This is the least common cause, which is worth saying because it is the one people want to believe first.
How to narrow it down in ten minutes
Unplug everything on the circuit. Reset once. If it trips instantly with nothing connected, leave it off and call the emergency line. If it holds, plug things back one at a time and see what brings it down: a single guilty appliance is a cheap fix. If it only trips when several things run together, it is an overload, and the question becomes whether the circuit, or the panel behind it, matches how you actually live now.
When it is urgent
A trip with a burning smell, a hot outlet or switch plate, scorch marks, or any buzzing from the panel is not a diagnostic exercise. Leave the breaker off and call. And the rule underneath all of this: never replace a breaker with a bigger one to stop the tripping. The breaker size protects the wire in the wall, and defeating it is how a nuisance becomes a fire.